Injection method of molding thermosetting material



E. E. NOVOTNY 2,356,081

INJECTION METHOD OF MOLDING THERMOS-ETTING MATERIAL Aug. 15, 1944.

Filed Feb. 8, 1940 INVENTOR EMIL. E. NOVOTNY ATTORNEY Patented Aug. 15,1944 UNITED STATES PATENT, .OF-FlCE mmorioN METHOD or MOLDING,rnmmosnmmc MATERIAL Emil E. Novotny, Philadelphia, Pa., assignor toDuritc Plastics, Incorporated, Philadelphia, Pa., a corporation ofPennsylvania 1 Application February 8, 1940, Serial No. 317,811 (01.18-55) 16 Claims.

the same through-an orifice in a superheating block where there isimparted to the material a suiilcient amount of heat and where anexothermic reaction is initiated, the superheated material being forcedtherefrom into the mold which latter is heated at a lower temperaturethan the superheating block to prevent burning and charring of themolded piece, the mold giving form and mold finish and preventing unduecooling of the heated material, the molded piece then being ejected fromthe'mold while retaining sufflcient exothermic heat to cure afterejection to its final ultimate form.

By'my method the pressure chamber need be only large enough to take careof the molding requirements of a single mold'cavity charge; the plungerof the pressure chamber may be relatively of small diameter to provide ahigh unit pressure. This unit pressure is only necessary to provideinjection motion and need not be maintained during the period of cure,since pressure within the mold cavity is maintained by the cur- 7 ing ofthe thermosetting material within the oriflce of the superheating block.As the mold is only formative and provides a set film on the moldedpiece of no great depth at the surface of the mold cavity, the-formed ormolded piece is not cured therein, but may be immediately ejected fromthe mold after the setting of a surface film.

' A relatively high per diem production may be obextent that it is moreeconomical in the molding of pieces of ordinary design to use multiplecavities and the compression method.

On the contrary, great strides have been made in the molding ofthermoplastic materials, particularly cellulose acetate, as this producthas a rather definite softening or plasticity temperature, and in thepressure chamber the product is heated only to this point of plasticityand is then forced into heated and/or cooled mold cavities where only aslight temperature drop sets the pieces to sufficient rigidity to beejected quickly from the cavity. If one of the steps in the molding ofthese thermoplastics called for a cure under conditions of heat andpressure within the mold, then the operation would be. slowed up somaterially as to be ordinarily non-competitive with multiple cavitycompression molding.

Thermosetting materials, however, set up at temperatures below theirtemperature of optimum plasticity and therefore cannot be held at thistemperature for a commercial length of time without becomingsubstantially non-flowing; The products, furthermore, are poor heatconducting mediums and therefore absorb heat in thin films, particularlywhen not compressed, and when compresed to provide a solid bodytheproducts react exothermically at a higher rate of' speed than whennot compressed. It is therefore advantageous to induce plasticity priorto compression, and it is equally advantageous to maintain this optimumplasticity by retaining the absorbed plasticizing heat therein. Whenfully compressed and forced through a relatively small orifice in a zoneof high temperature the materials rapidly take on heat suflicient tocarry the exothermic reaction to completion as ejected from such hightemperature zone, and if such ejected parts are not allowed to coolmaterially until tained from a single mold cavity, as the pieces neednot be cured nor cooled, as industrially un-' a relatively low per diemrequirement, or to pieces where the design of the part. is such that itwould be diflicult to mold satisfactorily by the usual compressionmethod of molding. This has been so because thermosetting materials,such as synthetic resins, require a definite cure and this slows downthe molding cycle to such an appreciable the exothermic reaction hasbeen substantially completed. on this basis, therefore, it is possiblemy U. 8. Patent 1,319,107, filed December 18,

1916, issuedOctober 21, 1919. In this patent, compounds of Bakelite orCondensite type were a; to $4; in. thickness of rather uniformly groundpressure chamber was detachably mounted on they mold, was heatedthereby, and suflicient heat was provided to set the material in themold to its final ultimate infusible form. The mold cavity was alsoprovided ,with restricted outlets to prevent the building up ofexcessive pressure within the mold cavity, The unit was used primarilyin the molding of printing plates having a more or less endless design,and reproduced with fidelity the regularities of the printing face andthe irregularities of the non-printing surface. The method and apparatuswas primarily designed for the handling of a single molding of a partwhich would have been most difilcult to mold by ordinary compressionmethods. The method,

however, would not be used in competition with ordinary multiple cavitycompression molding' methods, but was admirably suited for th molding ofparts which could not be molded except with great difllculty by means ofthe compression method.

In my U. S. Patent 1,993,942, filed February 16,

1929, issued March 12, 1935, an injection method.

andapparatus is shown which functions automatically for a number ofrepeat moldings. This apparatus, likewise, calls for the cure within themold and therefore was not intended as a method competitivelyadvantageous over the then existing method of compression molding, butwas likewise designed for the purpose of molding certain particular workwhich it would have been difficult to mold by such compression methods.In this apparatus the pressure chamber is utilized for the purpose ofplasticizing, the pressure chamber must be heated to a relatively hightemperature to quickly plasticize materials coming into contact with thesurface of such temperature, and therefore the temperature therein isnot merely the temperature required to obtain optimum plasticizingconditions, but a maingranular material is heated to its optimumplasticizing temperature. This heating is done in relative smallquantities continuously'and in relatively thin films, and is preferablyfed over a corrugated surface, thus causing the particles to mix androtate and acquire a uniform temperature throughout.

The plasticizing temperature cannot be definitely given as this willvary with various types of molding compositions. Variousphenol-aldehyde, urea-aldehyde, etc. resins have various plasticizingtemperatures and consideration must be. given the temperature requiredfor plasticizing. There may of necessity be a closely ad- .lustedbalance between the material needs as to plasticization and cure and thetemperatures used, being guided likewise by the decompositiontemperature of the material intended for use. Considering, however, onetype of resinous material containing cashew nut shell oil as thereacting phenolic body, an optimum plasticizing temperature ofapproximately 200 F. is advantageous; At the temperature of 200 F. thisprod uctQknown as Durite S-2208, for a period of six minutes willmaintain a flow of 93% (Durite Plastics flow. standards), at a unitpressure of 10,000 lbs/sq. in. When the material is heated for a periodof ten minutes the fiow under these conditions is only 88%; at the endof fifteen minutes it is 76.4%; at the end of thirty minutes 153%; andat the end of one hour 8.2%. While in conjunction with the type of workdone and tained temperature high enough to force a sufficient quantityof plasticized material into the mold cavity without undue loss of time.That is, in the operation of this unit the material flows only asrapidly as it is plasticized; and being a poor conductor of heatplasticizing occurs from surface contact with the heated pressurechamber and therefore maximum velocity through the injection orifice isnot merely the result of size of the orifice, its resistance andpressure applied. Therefore mold cavities by this method are filled moreslowly than need be. In order, furthermore, to carry a sumcient amountof material the pressure chamber must be of relatively largediameter-and/or cumbersomely long, and therefore it is difiicult toprovide high pressures to assist in the rapid flow of material and keepwithin reasonable thicknesses of side walls of the pressure chamber andthe construction of the pressure producing source such as the operatingram.

The method of my present invention offers distinct advantages in therapid molding of thermosetting compositions, some of the characteristicsthe velocity of pressure used in injecting the material into the moldcavity,

2. The material plasticized in its loose granular form is fed to theloading well or hopper of the pressure chamber or injection cylinder andthe hopper and cylinder are heated to prevent undue cooling of theplasticized material to a temperature below the plasticity required forthe production of particular parts. It is to be understood, of course,that even elevating the temperature within the pressure chamber is notobjectionable should there be a drop in the temperature of thecomposition, for instance held in the loading well or if for otherreasons. The temperature, however, should not be so high as toprematurely initiate exothermic reaction to the point of setting up-thematerial to infusibility within the pressure chamber. Specifically,working with Durite 8-2208 the temperature of the molding powder issuingfrom the heating conveyor, stored in the loading well, and transferredto the pressure chamber should be substantially uniform, and atpreferably about 200 F. with a maximum of not to exceed 250 F. Ofcourse, if the pressure chamber material is being rapidly ejected theprecaution here is to maintain the temperature to eliminate burning,charring, discoloration or a premature set condition. However, if theapparatus should be held idle and the temperature of the pressurechamber should be however, is sufficiently high to provide aninstanhigh, then a special ejector should be placed on the plunger toforce all of the material positively out of the chamber to preventclogging. Where, the material in the'pressure chamber is maintained atapproximately 200 F. and a unit pressure of 10,000 lbs./sq. in. isavailable, it has been found the material in the pressure chamber wouldflow, where Durite S-2208 is used, even after holding a charge thereinfor a period of one hour, as during the lunch period.

3. The now plasticized material is forced through an orifice-within thesuperheating block, this block having an adjustable mounting on Iorifices of the superheating block and the mold,

the mold itself. This superheating block may be heated at varyingtemperatures, the temperatures being so adjusted that thematerialfeeding through its channel will acquire a temperature sufiiciently highso that not only an exothermic reaction ensues, but that sufficient heatis stored up in the material to carry the reaction through toinfusibility. This superheating block, heated to various temperatures,may be heated to a somewhat lower temperature at the orifice leadingfrom the pressure chamber so as to minimize the effect of conducted heatfrom the superheating block to the pressure chamber orifice. If thepressure chamber at the orifice end is heated efiiciently with hot wateror atmospheric steam and pressure is not allowed to build up, thetemperature of this orifice may readily be maintained at the boilingpoint of water. The

temperature requirement of this superheatingv block is dependent uponthe length of such orifice in the block, the velocity of the materialbeing fed through such orifice the temperature tolerance of the materialbeing fed and the heat needed to provide infusibility through the cureoutside the mold cavity. With Durite S-2208 the material in the orificewould be heated to a temperature of from 400 to 650 F., depending on thetype of filler used. Ordinarily the superheater block is to be heatedfrom 500 to 1000 F. when utilizing a material such as Durite 8-2208 andfor that matter most phenol-aldehyde molding compositions. Thesuperheating block can be built up in sections; certain sections may beat higher temperatures than other to provide a product heatedsufiiciently to permit of final cure without requiring a long heating inthe mold cavity. The superheating block maybe electrically heated toprovide a temperature sufiiciently high to provide a high heat transferrate due to a high heat potential differential. However, as stated, theblock may merely be heated with atmospheric steam in a section bearingagainst the extrusion cylinder orifice, preferably with steam atatmospheric pressure, or with hot water, to thereby absorb the surplusheat of the highly heated portion of the superheating block and removethe same in the form of latent heat of vaporization, thereby maintainingthe temperature of required plasticity within the pressure chamberorifice. Details of manipulation will be readily apparent to thosefamiliar with the molding of thermosetting resinous compositions andtheir temperature tolerances.

4. Withthe first molding piece this superheated plastic material entersthe mold cavities by means of well known gates (but first fills aninfusible plug cavity which communicates with the mold cavities). Theproduct is formed in the mold, and at the reduced temperature of themold the materialforming the surface is rapidly'cooled to the surfacetemperature of the mold cavity which,

and with the second molding operation such infusible material is forcedinto the cavity provided for the infusible plug, and this infusiblematerial is then ejected with such subsequent molded piece.

5. It should be noted that so soon as the mold has been filled and themotion of the plastic material has ceased that the material in thesuperheating block channelor orifice is set to infusibility, locking thepressure within the mold cavity. The plunger of the pressure chamber maybe withdrawn for a preferred distance or a distance suflicient toprovide a new charge of material (the single shot operation is much tobe preferred, but several moldings from one pressure cylinder is notprecluded) and simultaneously the superheating block may be pulled awayfrom communication with the pressure chamber ori-' fice, and continuingof the stroke will cause ejection of the piece and the ejection of thepreviously formed infusible gate.

A description of the accompanying drawing, all of which is in schematiccross section, is made herein for a better understanding of myinvention. Figure 1 is an elevational view, in section, illustrating aninjection unit comprising the essential steps of my invention. In thisillustration the mold cavity is closed, the superheating block 'is inposition, the pressure chamber is receiving additional material and isnow ready for the forward stroke to force a measured quantity ofplasticized material into the mold cavity.

Figure 2 is a view showing the mold cavity closed and filled, with thesuperheating block still against the pressure chamber orifice;

Figure 3 is a view likewise in cross section showing the mold open, thesuperheater block removed from the pressure chamber orifice andReferring now more in detail to the drawing,

Figure 1 diagrammatically illustrates the operation of a suitablemolding press which may be used to practice the process of my invention.A is a main feed hopper which holds any quantity of a granular moldingcompound, provided with a gate G, the said feed hopper being supportedabove a heated conveyor B. Molding compound C issues from the hopper Aand travels over the heated conveyor B. The heated conveyor B has aheating surface D which may be smooth,

but preferably is corrugated or" fluted as shown. The purpose of thecorrugations is to thoroughly mix and bring all particles of thegranular molding compound into equally close proximity to the heatedsurface. E representsa known type of vibrating meansof high frequencywhich is made.

a part of the conveyor itself. (Such a vibrating is indicated at N, andthis together with the vibration and rate of feed is so adjusted as toprovide a material of optimum heat plasticized condition emptying intohopper H.

Where Durite S-2208 is used, the rate of feed to theconveyor should besuch as to plasticize the product, at the rate of delivery needed, to atemperature of between 200 and 250 F. The corrugations D may be ofhighlypolished material and where infra-red lamps mounted on cover F providedwith a suitable reflector are used as supplementary heating it ispreferable to have the reflector and the heating surfaces of theconveyor plated with polished gold, for example, which will reflect mostof the heat rays into and through the molding composition. As to thecapacity of the conveyor, usually one of 12 in. width with a length offrom 2 to ft. may be used, depending upon the amount of materialrequired and'the facilities used for heating. Under ordinary moldingconditions one cubic foot or 40 be electric, with the exception that atthe orifice pounds of molding compound per hour, utilizing devices,gates or measuring devices to check the.

measured feed of the conveyor and thus provide a definite portion ofmaterial for each charge. Such devices are well known and are not shown.

The plunger for the pressure chamber is indicated at I-J. The plunger is-likewlse provided with a self-packing annular ring to obviate thenecessity of providing a close fitting plunger and as this plungermatches up in contour with the farthest end of the pressure chambercavity, to permit the forcing out of any excess material should theyremain idle or for some other reason,

it is desirable that the plunger limiting collar or other device beclosely adjacent to prevent abnormal pressure of metal to metal at thefar end of the operating stroke. Material is dropping in measuredquantity from the loading well H into pressure chamber cavity L inreadiness for the next injection stroke. The pressure chamber as anentirety is shown at K, the orifice thereof at M, and the heating means,again conventionally, is shown at N. It is to be understood that thisheating means is purely optional and that withproper insulation andproper initial heating through use it is generally possible to dispensewith heating. altogether, the precaution being to maintain-the moldingcompound C at its op timum plasticized condition throughout the cavity Land the orifice M. The heating means here,

M, where, if any heating means is used, it should preferably be of sucha nature as to act more as a cooling medium, and thus hot water oratmospheric steam could be used, which would then prevent a temperaturerise much beyond the boiling point of water or much beyond thetemperature of the molding compound C.

At 0 the superheating block is shown. A number' of sections may beprovided, two being shown. The function of this superheating block is toimpart a sufficiently high temperature to a relatively thin stream ofinjected material traveling through the block orifice P as to providesuflicient heating to initiate exothermic reaction and to provide asufficient amount of heat within the composition, this to permit thematerial to be cured through such absorbed heat and heat of reactionafter having been formed in the mold. Heating means Q for thesuperheating block 0 is only conventionally shown, and the block isintended to be heated to a high temperature which would be difficult toattain through the use of ordinary steam pressures available, andtherefore electric heating is recommended, with a sufficient wattageinput to heat at least the latter end of the plug to a relatively hightemperature in the order of from 600 to 1000 F. The part of the plugadjacent to the pressure chamber orifice may be heated with atmosphericsteam if a supersensitive material is used to prevent the transmissionof too much heat to the pressure chamber at this point. However, with'adequate removal of heat at the pressure chamber orifice this may bedispensed with, and particularly so if the mold cavity is quickly filledand the superheating block 0 is quickly withdrawn from the pressurechamber orifice, as indicated in Fig. 3. The pressure chamber blocksections are assembled and mounted on the mold or mold block by means ofa suitable mounting means such as indicated by means of bolts R. Thismounting may be on merely the rectangular surface of a mold block ormold, or the mold may be shaped with sufficient material removed topermit the assembly of the superheating block 0 more closely adjacent tothe mold cavity gates.

This superheating block, furthermore, is made adjustable so that thecavity or feed channel may be provided of any reasonable length by meansof bolting on additional units or removing units from the assembly.

The mold itself is indicated as an entirety at S, the separating orpartin line thereof at T and the cavities at U. The orifice for fillingthe' mold is indicated at V. The material within orifice V shown inFigure 1 has lost its superheat and isnot to be used together with theset material in orifice P in the next molding, but upon pressure beingapplied by plunger I this infusible.

material will be forced into the cavity indicated at X, in position forejection by the ejector Y when this material will be attached to thenext in orifices P and V whichupon the next subse- ,quent molding willbe forced into the cavity X. The material from the previous molding incavity X is now attached to moldgate W and is being ejected by means ofthe ejector Y. The molded a hard set condition after the machine hasstood idle for an unusual length of time, the material, whilestillplastic, may readily be ejected from the pressure chamber cavity L andorifice M by means of a' supplementary ejector I which may be placed onthe plunger I, as shown in Fig. 4. The use of such ejector is optionalas other means may be utilized, as by the ejection of certainthermoplastic material or by forcing the infusible material out of theorifice and out of the pressure chamber cavity L. a

Figure shows a modification of the mold S, indicated here-as S S S beingthe cavities thereof and S being restricted flow orifices to permit theflow of excessive pressure producing material from the mold cavity S Theoverflow edge is constructed somewhat along the lines of the cut offedge in flash type compression mold- The instant the material iscompressed in the mold cavity U the motion stops in orifices M, P and V,plunger I is reversed, the superheating block.O together with the moldis withdrawn and the material in the orifice P of the superheating blocki set sufiiciently to maintain the material under pressure within themold cavity U. In the next cycle, as soon as superheating block 0returns again in operative coincidence with the orifice M of thepressure chamber, the material in the orifice M is at that instant againin motion. This is stated here to stress the fact that the superheatingblock remains in position against the orifice M only during the timethat material is being forced into the mold cavity. This is done so thatdue to the high temperatures, the material does not set in orifice M'dueto superheating. This also provides the possibility of breaking thematerial at the junction of the pressure chamber and superheating block,as indicated in Fig. 3. In Fig. 3 the material previously remainingwithin orifices V and P is fragilely connected to the gate of the moldedpart W, whereby separation is readily made at this point.

The pressure superheating block while mounted on the mold at aconsiderable distance from the mold cavity, may be mounted partiallywithin the mold block by removing portions of the metal of the moldblock, whereby the superheatin block is brought into closer proximitythereto. The heating of the apparatus can be of any type, hot water,atmospheric steam, steam atrequired pressures, hot oil, but preferablythe heating would be done electrically, except perhaps the heating ofthe superheating block section adjacent to the pressure chamber orifice,which could most desirably be heated by means of-hot water oratmospheric steam, so as to absorb and remove excess heat rapidly. Thesame is true likewise of the heating of the pressure chamber casing. Themold and the conveyor if heated by steam would be heated to atemperature of approximately 330 to 350 F., Certain materials which willnot stand. a high mold temperature would call for a ower steam pressure,as for example urea molding compounds, which are likely to discolorseriously at temperatures above 280 F.

, pulverized material to maintain plasticity in the pressure chamber.

The various parts of the apparatus should be heat insulated. A covershould be used over the pressure chamber hopper. Various thermocouplesshould be inserted at points of required temperature information, suchas at the discharge point of the conveyor, the extrusion chamber hopper,the extrusion cylinder, the various sections 6f the superheating blockand closely adjacent to the mold cavity itself. These, in the well knownmanner, to be connected with recording and automatic temperature controldevices.

By thermosetting molding compositions I mean to include ready-to-usemolding compositions, or combinations of filler, fibre, plasticizer andresinous binder, thoroughly intermixed, to function as a moldingcomposition, or, for that matter, the resinous components themselves,and becoming more rigid through polymerization or chemical reaction sothey may be ejected from the hot mold without cooling. The usual typesof thermosetting materials are already well known and are represented bya large class of phenol-aldehyde resins. and similar resins of naturalderivation, such. as gum accroides, containing reactive phenolic (OH)groups, also various resins made from natural vegetable growthphenolic'bodies such as obtained from the group of trees known asAnacardiaceae, such as exemplified by cashew nut shell oil, Japaneselacquer, etc. In addition to the many phenolic resins,*resins of theurea type and of a thermosetting nature are included, likewise, the morereactive types of thermosetting alkyd resins, such for example as theglycol-maleic ester copolymerized with styrol or methacrylate resin orpolymers. The glycol-maleic ester when used alone without being alloyedwith other mutually operating conditions must be carefully ascertainedand maintained. Products of the thermosetting type of resinouscompositions oil'er full.

utility of my apparatus and method.

Various temperatures were given for the superheating of the'mo'ldingcompound in the orifice P of the superheating block 0. When using mostphenol-aldehyde resins and the special cashew heated at fromapproximately 600 to 1000 F.

and that the heat must be given off rapidly;

Where other fillers Therefore it is desirable that this block be made ofa metal of large cross sectional area, relatively to the size of thechannel for superheating. and be of such character as to be efllcient inheat transmission, and preferably on the outside should be heatinsulated. It is not essential that all of the contacting surface be incontact with the end of the pressure chamber K. As the material travelsthrough orifice P at high velocity and must take on a superheat of from200 to 300 F. ordinarily, the metal of this superheating block should bean efiicient conductor of heat. The orifice P should be long lasting andtherefore a plating or lining of this orifice P with a morewear-resisting or harder material of almost equal heat conductivity isadvised, such, as for example, iridium.

In the pressure chamber a high unit on the plunger I-J is to bepreferred to any increased temperature in the pressure chamber. Thispressure indicated in the given example to be about 10,000 lbs./sq. in.,may be anywhere from 10,000 to 50,000 lbs/sq. in.

The practice of the method of my present invention and the use of theapparatus employed therewith will be fully apparent from theabovedetailed description thereof. Th essential features of the same maybe here briefly summarized.

The thermosettingmaterials are plasticized in a thin granular stream. Inthis step of the method, the individual particles receive eql al heattreatment as they are fed over the conveyor which delivers the materialin a relatively thin stream and in a granular or powdery condition tothe pressure chamber. The thus delivered material is homogeneouslyplasticized by heat to a definite temperature. The material brought upto the plasticizing point is maintained in the preheated, preplasticizedcondition in the pressure chamber. supplied to this plasticized materialin the pressure chamber, the pressure chamber being heated if necessaryto merely maintain the temperature conditions of this plasticizedmaterial delivered thereinto. Therefore, at this stage of the processthe present invention advances a new practice in the molding ofthermosetting materials, in that complete and suillcient plasticizationby heat is given the granular or pulverized resinous material beforepressure is applied. This plasticizing to the full plasticity requiredfor complete flow separates the function of heating from the function ofpressure. As stated, no further heating is given to the preplasticizedmaterial in the pressure chamber. It is important to note that byplasticizing the individual granules or particle in the high frequencyvibrator conveyor treatment, a uniformity of heating is obtained whichcould not possibly be produced by heating a thick cross-section or amass of material. There is, therefore, produced a heating pressure Nofurther heat is block, and thence into the mold cavity. The

operation of the pressure chamber thus fluidizes the material, causingthe same to flow through the orifices and into and to fill the molcavity or cavities. It is during this fluid tra'isit that th material issuperheated by flowing through the superheating block.

The superheating block functions to elevate the temperature of thefluidized material which is being forced through it to a point ofsuperheating, whereby the material can subsequently be set by the heatwhich i absorbed by the material and by the exothermic reaction heatwhich is brought about by this superheating treatment, This heating ofthe fluidized material to a degree suilicientlyhigh and yet below itspoint of decomposition, by the use of the superheatin block and themovement of the material through a small orifice, with this superheatingblock heated to a temperature substantially higher than the temperatureof the mold, and then rapidly forcing this superheated material into themold cavity where the material is formed and the finish of the mold isreproduced, is the next essential feature of the process. It should benoted that this superheating of the material in a relatively thin streamthrough the superheating block, eliminates to a very large extent anygases which would be engendered during the major part of the exothermicreaction, since the reaction is already well on its way when thematerial enters the mold cavity.

As soon as the molded piece is given finish and form in the mold cavity,by effecting a cure of the external surface or layer of the moldedproduct, it is ejected from the mold into a suitable container forfurther curing. Thus no curing of the interior of the molded piece takesplace in the mold. For this purpose, the temperature of the mold issubstantially lower than the temperature of the superheating block, andwhile the mold cavity is heated at the lower temperature, thetemperature is high enough to promote continuing reaction.

The thus molded piece, after ejection from the mold, continues to reactunder the influences of the heat retained in the body thereof untilfinal cure is effected.

While I have shown the preferred steps of carrying out the process andwhile I have illustrated an example of apparatus to be used therewith,and while I have given some examples of materials, temperatures andmodes of treatment,

- it will be understood that these were given only uniformly ofindividual particles while in motion,

' by way of illustration and not by way of limitation. It will beobvious that many changes may be made in the step sequence and in theoperation of the apparatus, and ln the constructional design of theequipment. without departing from the spirit of the invention defined inthe following claims.

In the following claims, the expressions superheating" and superheatedshall be understood to mean heating or heated to temperatures above thetemperature at which the thermosetting material will cure.

I claim:

1. The ejection method of molding thermosetting materials which consistin heat plasticizing the material, in forcing the heat plasticizedmaterial through a superheating zone and thereby fluidizing andsuperheating the material, in filling a mold with the fluidized andsuperheated material to give form and finish thereto, in ejecting theformed but interiorly uncured piece from the mold and allowing themolded piece to core by means of its superheating acquired stored upheat to the insoluble infusible state after ejection from the mold.

2. The injection method of molding thermosetting materials which areexothermic in their curing reaction which consists in heat plasticizingthe material, in forcing the heat plasticized material through a'superheating zone and thereby fluidizing and superheating the material,the

material as it passes through the superheating zone acquiring atemperature sumciently high so that an exothermic reaction ensues, infilling a mold with the fluidized and superheated material to give formand finish thereto, in ejecting the formed but interiorly uncured piecefrom the mold, the ejected molded piece containing sumcient stored upheat acquired upon passage through the superheating zone to enablecuring to the infusible insoluble state to take place, and allowing themolded piece to cure after being ejected from the mold.

3. The injection method of molding thermosetting materials relativelysolid and granular at ordinary temperatures whichconsists in heatplasticizing the material while maintaining the same in a granularcondition, in forcing the thus heat plasticized material under pressurethrough a superheating zone and thereby fluidizing and superheating thematerial in filling a mold with the fluidized and superheated materialto give form and finish thereto, in ejecting the formed but interiorlyuncured and still thermoplastic piec from the mold, and allowing themolded piece to cure to the infusible insoluble state after ejectionfrom the mold.

4. The injection method of molding thermosetting materials whichconsists in heat plasticizing the material, 'in forcing the heatplasticized material through a superheating zone and thereby fiuidizingand superheating the material, the material as it passes through thesuperheating zone acquiring a relatively high temperature, iii filling amold with the fluidized and superheated material to give form and finishthereto, the molded piece containing sufllcient stored up heat acquiredupon passage of the material through the superheating zone to enablecuring to take place, and allowing the molded piece to cure after beingejected from the mold.

5. The injection method of. molding thermosetting materials relativelysolid and granular at ordinary temperatures which consists in heatplasticizing the material while moving the same in a thin layer andmaintaining the same in a granular condition, in forcing the thus heatplasticized material through a superheating zone and thereby fluidizingand superheating the material, in filling a mold with .the fluidized andsuperheated material to give form and finish thereto, and in ejectingthe formed but interiorly uncured and still thermoplastic piece from themold, and allowing the molded piece to cure to the infusible insolublestate after ejection from the mold.

6. In the injection method of molding thermosetting materials, the stepswhich consist in forcing a heat plasticized thermosetting materialthrough a superheating zone and thereby fluidizing and superheating thematerial, in filling a mold with the fluidized and superheated materialto give form and finish thereto, the molded piece containing sumcientstored up heat acquired upon passage of the material through thesuperheating zone to enable curing of the molded piece to take place,and allowing the molded piece to cure after being ejected from the mold.

'1. In the injection method of molding thermosetting materials which areexothermic in their curing reaction, the steps which consist in forcinga heat plasticized thermosetting material through a superheating zoneand thereby fiuidizing and superheating the material, the material as itpasses through the superheating zone acquiring a temperaturesufiiciently high so that an exothermic reaction ensues, in filling a-mold with the fluidized and superheated material to give form andfinish thereto, the molded piece containing suillcient stored up heatacquired upon passage of the material through the superheating zone toenable curing of the molded piece to take place, and allowing the moldedpiece to cure after being ejected from the mold.

8. In the injection method of molding thermosetting materials, the stepswhich consist in forcing a heat plasticized thermosetting material'through a superheating zone and thereby fluidizing and superheating thematerial, in

filling a mold with the fluidized and superheated material togiveformand finish thereto, in ejecting the formed but interiorly uncuredpiece from the mold, the molded piece containing suflicient stored upheat acquired upon passage of the material through the superheating zoneto enable curing of the molded piece to take place, and allowing themolded piece to cure after being ejectedjrom the mold.

9. Inthe injection method of molding thermosetting materials relativelysolid at ordinary temperatures, the steps which consist in forcing athermosetting material through a superheating zone and therebyfluidizing andsuperheating the material, in filling a mold with thefluidized and superheated material to give form and finish thereto, inejecting the formed but interiorly uncured piece from the mold, themolded piece containing suflicient stored up heat acquired upon passageof the material through the superheating zone to enable curing of amolded piece to subsequently take place and allowing the molded pieceto'cure afterbeing ejected from the mold.

10. In the injection method of molding thermosetting materialsrelatively solid at ordinary temperatures, the steps which consist inforcing a thermosetting material which is exothermic in its curingreaction through a superheating zone and thereby fluidizing andsuperheating the ma-\ terial, in filling a mold with the fluidized andsuperheated material to give form and finish thereto, the material as itpasses through the superheating zone acquiring a temperaturesufficiently high so that an exothermic reaction ensues, in ejecting theformed but interiorly uncured piece from the mold, the molded piececontaining suflicient stored up heat acquired upon passage of thematerial through the superheating zone to enable curing of a moldedpiece to subsequently take place, and allowing the molded piece to cureafter being ejected from the mold.

11. In the injection method of molding thermosetting materialsrelatively solid at ordinary temperatures, the steps which consist inforcing a thermosetting material through a superheating zone and therebyfluidizing and superheating the material, in filling a heated mold withthe fluidized and superheated material to give form and finish thereto,the heated mold being held at a temperature substantially below that ofthe superheating zone, in ejecting the formed but interiorly. uncuredpiece from the mold, the

' molded piece to subsequently take place, and allowing the molded pieceto cure after being ejectedirom the mold.

12. In the method of molding thermosetting materials relatively solidand granular at ordinary temperatures the steps which consist in heatplasticizing the thermosetting material while moving the same in a thinlayer at such a speed as to prevent any substantial advancement of thethermosetting material and maintaining the same in a granular andparticle flowing condition, and in then applying pressure withoutfurther heat to the thus plasticized granularv material to fiuidize thesame.

13. In the method of molding thermosetting materials relatively solidand granular at ordinary temperatures the steps which consist in feedingthe thermosetting material in a thin layer over a conveyor vibrated athigh frequency, the said material being fed at such a speed as toprevent any substantial advancement thereof, in heat plasticizing thematerial as it is fed over the conveyor while maintaining the materialin a granular and particle flowing condition, and in then applyingpressure without further heat to the thus plasticized granular materialto fluidize the same.

14. In the method of molding thermosetting materials relatively solidand granular at ordinary temperatures the steps which consist in feedingthe thermosetting material" in a thin layer over a conveyor, the saidmaterial being materials relatively solid and granular at ordinarytemperatures the steps which consist in heat plasticizing the materialwhile maintaining the same in a granular and particle flowing condition,in then applying ressure without furtherheat to the thus plasticizedgranular material to fiuidize the same, and in then forcing thefluidized material through a superheating zone.

16. In an injection method'of molding thermo setting materials, thesteps of forcing a superheated and fluidized thermosetting material intoa heated mold cavity held at temperatures substantially below thesuperheated material, the material being given form and finishby themold, and in quickly ejecting the formed but interiorly uncured and hotmolded piece from the mold,

the superheat in the material and molded piece being sufllcient forcuring the piece, and allowing the molded piece to cure after beingejected from the mold.

EMIL NOVOTNY.

